The invention relates to a device and a method for storing electrical energy in vehicle batteries in vehicles.
Vehicles are increasingly being driven by electric motors. To achieve this, an electrical charge or electrical energy is charged in a vehicle battery, which supplies consumer units with current, in particular an electric motor of the vehicle, when the vehicle is in travel operation mode. Increasingly, also, energy or current is being fed into the public mains network which derives from wind power systems. The power available in the mains network is therefore subject to fluctuations which are dependent on the amount of the wind current being fed in. In order to reduce such fluctuations it is necessary for these current fluctuations to be buffered in separate current storage units, which are connected to the network, and for superfluous current to be stored intermediately.
It was therefore proposed to use vehicles as mobile current storage units, as reported in Pictures of the Future, Autumn 2009, pages 44-46, “Electric automobile in the Smart Grid” (http://wl.siemens.com/innovation/de/publikationen/pofherbst200/energie/ecar.htm), wherein consideration is given to vehicles being electrically refueled in a public mains network in order to take up windpower current. If in this situation the demand for current is high, current will be fed back from the vehicles into the network. The vehicles accordingly serve to compensate for fluctuations which are caused, for example, by windpower current. The vehicle batteries in the vehicles make their storage capacity available to the mains network, in order to buffer current or power fluctuations respectively.
A disadvantage with these conventional storage devices is, however, that the vehicle keeper does not have complete control of the load charge state of the vehicle battery contained in his vehicle. If, for example, the vehicle battery of the keeper's electric vehicle connected to the mains network is discharged due to a high demand for current in the mains, then the electrical charge remaining in the electric vehicle's battery may no longer be sufficient, under certain circumstances, for the purposes of the vehicle keeper. For example, if the vehicle keeper or driver wishes to drive away from the electricity tapping column, by which the electric vehicle is connected to the mains network, in order to reach a destination, it may occur that, due to the discharge of the vehicle battery, incurred by the high demand for current in the mains network, the remaining electrical energy or charge stored in the electric battery will no longer be sufficient to reach the destination. In this case the driver would be compelled to charge up the vehicle battery before starting the journey, which would require a certain and not inconsiderable charging time. In this case the driver would therefore be compelled to wait until the vehicle battery had reached the required charge state before being able to depart for the destination.